Conventionally, electric vehicles that are driven by a driving force of an electric rotating machine such as a motor generator, hybrid vehicles in which an engine which is an internal combustion engine and an electric rotating machine are used in combination, fuel cell vehicles that driven by electric power generated by a fuel cell, and the like have been known. These vehicles include a power control device having a boost converter, an inverter, and so on, that receives electric power supplied from a main battery or a fuel cell and controls electric power to a motor generator (hereinafter also referred to as a “motor”).
The power control device is also referred to as a PCU (power control unit). As the PCU deals with high voltage and high current, it is necessary to mount the PCU in an engine compartment near the motor generator. Accordingly, in a hybrid vehicle in which an engine is started by a motor generator, because an auxiliary battery for starting the engine does not supply electric power to a cell motor and therefore need not be placed near the engine, and in order to maximize space for disposing the PCU in the engine compartment, the auxiliary battery is disposed in a luggage compartment.
In recent years, with advancements in downsizing of high-voltage instruments, it has become possible to place the auxiliary battery within the engine compartment and near the power control device. For example, Patent Document 1 discloses technology of fixing, on a transaxle (also referred to as a motor case) which includes a first motor generator forming a twin-shaft, a second motor generator arranged parallel to an axial line of the first motor generator, and a differential gear arranged on a third axial line parallel to the twin-shaft, a power control device that drives the first motor generator and the second motor generator, which is achieved by downsizing the power control device. With the use of this technology, it is possible to realize downsizing of the power control device and simplification of wiring.
However, in a case in which an auxiliary battery is disposed near a power control device, it is necessary to avoid interference between the auxiliary battery and the power control device in order to perform protection and rapid discharge of the power control device smoothly at the time of vehicle collision in accordance with the regulations for at the time of collision (FMVSS305: Federal Motor Vehicle Safety Standard) of the National Highway Traffic Safety Administration (NHTSA) of the Department of Transportation in the United States. Accordingly, Patent Document 2 discloses a structure having a disengagement mechanism in which, at the time of vehicle collision, due to a load transmitted from an auxiliary battery via a guide surface, which is caused by backward movement of the auxiliary battery with the intrusion of a barrier (obstacle), a relay box moves upward and is separated from a vehicle body. With this mechanism, the battery moves backward smoothly. With such a disengagement structure of the relay box, it is possible to prevent interference between the vehicular instruments and other members that would move as a result of a collision impact and to thereby enhance the impact absorbing effect.
Further, while the auxiliary battery has a relatively low voltage of 12 volts and therefore damages caused by breakage are not significant, it is desired that damages to the power control device that controls a high voltage such as several hundred volts should be minimized. Accordingly, Patent Document 3 discloses an instrument-mounting structure in which, in order to protect the power control device itself at the time of vehicle collision, the power control device is mounted such that the front end of the power control device is located further toward the vehicle's rear side with respect to the front end of the transaxle and a motor compressor is placed toward the vehicle's rear side with respect to the power control device, and the auxiliary battery is mounted at the same position of the power control device thereby facilitating protection of the auxiliary battery.
Further, Patent Document 4 discloses an inverter disengagement mechanism which, in order to protect a power control device itself such as an inverter, causes the inverter and an inverter bracket to be disengaged from an inverter tray attached to a front member when an external force is applied to the inverter at the time of collision.